Aerosol cans have various structures, and an example is one having a bottom made of steel which is seamed to a can body. FIG. 1 illustrates the structure of an aerosol can to which a bottom is attached. A bottom 1 to be attached to the aerosol can illustrated in FIG. 1 is made from a circular blank, which is stamped out from a material. The blank is formed into a specified shape by press forming and seamed to a can body 2 using a flange formed in the peripheral portion thereof. A mounting cap 3 and a spraying nozzle 4, which have a function of spraying the content of the can, are also attached to the can body 2.
Since propellant, which is used to spray the content of an aerosol can, is enclosed in the can, the inside of the can is in a state of high pressure. Therefore, it is necessary that the bottom of the can have a sufficiently high resistance to pressure in order to withstand the internal pressure.
Techniques described below have been disclosed as techniques regarding a steel sheet to be used for a can of which a high resistance to pressure is required as is the case with an aerosol can.
Patent Literature 1 discloses a material steel sheet with surface treatment to be used for a DI can having high resistance to pressure and necking formability and a method for manufacturing the steel sheet. It is disclosed that the steel has a chemical composition containing, by mass %, C: 0.0100% to 0.0900%, Mn: 0.05% to 1.00%, P: 0.030% or less, S: 0.025% or less, sol.Al: 0.010% to 0.100%, N: 0.0005% to 0.0120%, and the balance being iron and inevitable impurities, that the material steel sheet has a grain size number (hereinafter, called G.Sno) of 9.5 or more, Hv (10% BH) of 145 or more, and Hv (70% BH) of 195 or less, that an annealed sheet having a G.Sno of 9.5 or more and an axis ratio of 1.4 or less is made by the steel having the chemical composition described above being subjected to hot rolling under a condition of CT: 660° C. to 750° C., cold rolling under a condition of a rolling reduction ratio of 84% to 91%, and box annealing under a condition of an annealing temperature: recrystallization temperature to 700° C. and that Hv (10% BH) is adjusted to be 145 or more and Hv (70% BH) is adjusted to be 195 or less by performing temper rolling on the annealed sheet under a condition of an elongation of 2% or more and 30% or less.
Patent Literature 2 discloses a steel sheet to be used for a DI can having a high resistance to pressure and necking formability and a method for manufacturing the steel sheet. It is disclosed that the steel sheet is a steel sheet to be used for a DI can having a chemical composition containing, by mass %, C: 0.01% to 0.08%, Mn: 0.5% or less, Sol.Al: 0.20% or less, and N: 0.01% or less, and, further as needed, containing one or more of S, Cr, Cu, and Ni: 0.1% or less and/or one or more of Ti and Nb: 0.1% or less, in which the content of solid solute C is adjusted to be 5 ppm to 25 ppm, in which the YP in the L direction is adjusted to be 30 Kgf/mm2 to 44 Kgf/mm2, and in which the difference in YP between the L and C directions is adjusted to be 2 Kgf/mm2 or less and that the method includes cold-rolling a hot-rolled sheet having the chemical composition described above, performing a recrystallization treatment, cooling the sheet at a cooling rate of 60° C./s or more, holding the sheet at a temperature of 300° C. to 450° C. for a duration of 30 seconds to 180 seconds, and performing wet temper rolling under a condition of a rolling reduction ratio of 3% to 12%.
Patent Literature 3 discloses a steel sheet to be used for a DI can having a low incidence of occurrence of cracks when a flange is formed and providing a can with high strength as a result of hybridization of a microstructure having crystal grains of a large size, which is advantageous for formability, and a microstructure having crystal grains of a small size, which is hard and has high grain boundary strength, and a method for manufacturing the steel sheet. The steel sheet to be used for a DI can according to Patent Literature 3 has a chemical composition containing, by mass %, C: 0.01% to 0.08%, Al: 0.03% to 0.12%, and N: 0.001% to 0.008% and a dual-phase microstructure classified in terms of grain size number according to JIS in the cross-sectional direction of a product sheet, one phase having a small grain size of #11.5 or more expressed as a grain size number and constituting portions of 5% to 25% in the thickness from the front and back sides, another phase having a large grain size of less than #11.0 expressed as a grain size number and constituting the remainder in the middle in the thickness direction. The disclosed method for manufacturing the steel sheet includes using a continuously cast slab as a material, heating the material so that the temperature of the surface layer portion is higher by 20° C. or more in comparison to that of the central part and the surface temperature is 1000° C. to 1200° C. and then performing hot rolling.
Patent Literature 4 discloses a steel sheet with both of good resistance to deformation of a can made of an ultra-thin steel sheet for can and good can formability and a method for manufacturing the steel sheet. The disclosed method includes cold-rolling steel having a chemical composition containing, by mass %, C: 0.0800% or less, N: 0.0600% or less, Si: 2.0% or less, Mn: 2.0% or less, P: 0.10% or less, S: 0.05% or less, Al: 2.0% or less, and the balance mainly including Fe, adjusting, for example, an atmosphere, a temperature, and a duration of a recrystallization annealing or a heat treatment thereafter and performing an appropriate surface treatment prior to the heat treatment so that change in N content in the steel, in particular, N content and hardness of the surface layer portions and the central layer portion, and further, of some part viewed from the surface of the steel sheet, are controlled respectively to values within different appropriate ranges.
Patent Literature 5 discloses a steel sheet with both of good resistance to deformation of a can made of an ultra-thin can steel sheet and good can formability and a method for manufacturing the steel sheet. The disclosed method relates to a steel sheet to be used for a two-piece can, and the method includes hot-rolling, using a common method, a continuously cast slab having a chemical composition containing, by mass %, C: 0.02% to 0.08%, Si: 0.02% or less, Mn: 0.05% to 0.30%, P: 0.025% or less, S: 0.025% or less, N: 0.003% to 0.02%, Al: 0.02% to 0.15%, and the balance being Fe and inevitable impurities, coiling at a temperature of 570° C. to 670° C., in which content of (Ntotal−NasAlN) is 0.003 to 0.010 mass %.